Stabilized silver halide emulsions



' Patented Sept. 25, 1945 UNITED STATES PA'T'ENT. -m

STABILIZED SILVER HALIDE EMULSIONS Fritz to York, N.

W. H. Gen

I No Drawing. Appli eralAnlllne {Film cation Serial No. 5433' Mueller, Binghamton, N. Y., assignm- Corporation, New

Y a corporation of Delaware 9 Claims. (Cl. 95-7) This invention relates to the improvement of photographic emulsions the incorporation Of antifogging or stabilizing agents into silver halide emulsions.

A large number of substances have been described'as being effective in'preventing an inand more particularly to crease in fog and thus stabilizing or controllingphotographic emulsions.

In-U. s. P. 2,057,764 there is described sprocess of stabilizing photographic silver halide emulsions by incorporating sulfinic or seleninic acids or their salts into the emulsion in the form of a solution in a suitable solvent during the preparation of the emulsion or by incorporating the stabilizer into the finished emulsion by'bathing the emulsion layer with a weak solution of the stabilizer. It is stated that the fogging influence of supports, preparation layers, backing layers, intermediate -layers, sublayers, protective layers,

. or baryta layers could be prevented by incorporating these stabilizers into such layers. As compared with films which were not provided with the sulfinic acid or seleninic acid stabilizers, it is stated that the films containing the stabilizer showed a fog density unit of approximately one-half. It has now been discovered that the stabilizing effect of the sulfinic or seleninic acids or their salts, disclosed in U. S. P. 2,057,764, can be consider-' ably improved and the range of application greatly extended if small amounts of certain diamino or N-heterocyclic, monoor polysulfides are present in the emulsions containing the sulfinates or seleninates. The particular mono and polysulflde compounds which produce this improvement are those which are in the class consisting of aryl-substituted diamino and N-heterocyclic mono and polysulfldes having the following structural formulae:

wherein It stands for an and radical, R: a memher of the group consisting of hydrogen, alkyl and aryl, n is a whole number equal to at least 1, Y

is a memberof the group consisting of N, O, S,

and CH:- and Z the remaining component groups or hetero atoms necessary to complete a 5 or 6-membered heterocyciic ring. It .has been observed that extremely small quantities of these mono or polysulfldes will improve the stabilizing characteristic of photographic emulsions containing a sullinate or seleninate to anLextent unobtainable with a sufinate or a seleninate alone. Thus, forvexample, the photographic eifect of sodium sulfinate 'or seleninate is improved bythe addition of 0.00025- 0.005() mol of the following sulfides per mol of sulfinate or seieninate:

Morpholine sulfide Morpholine disulfide Morpholine trisulflde Piperidine tetrasulflde Proline disulfide Morpholine tetrasulflde N-N'-di-thioaniline The remarkably improved result, expressing fog in terms of density units, is manifested in-a reduction of the fog density to a value of t the fog density obtainedwhenusing a sulfinate or seleninate in accordance with the process of U. S. 1. 2,057,764. Thus, freshly coated films having a fog density of 25 to 30 density units are reduced to a fog density of from 12 to 15 density units and films, incubated for 6 days at at 50 C. lowing a fog density of 25 to 35, are reduced to a fog density of 15 to 19 by adding morpholine 'disulfide in the above proportion.

.This reduction in fog density produces better elearness, better heating quality and an unusual brilliance which is especially desirable in medical and industrial radiographs.

The same reduction in fog density is obtained whether the mono or polys'ulfide compound is ,added with the sulfinate or seleninate during the ripening stage in the process of making. the silver halide emulsion or during mixing of the molten emulsion prior to coating or whether a solution of the sulfinate or seleninate to which hasbeen added a small amount of the sulfide is applied to the cast film as an after-coating. In

the latter case, solvents for the stabilizer mixture are employed which do not affect emulsions such as water or organic solvents whichtare miscible with water, for instance, alcohol. The stabilizin mixture of the sulfinic acid salt or seleninic acid salt and the mono or polysulfide compound may also be employed in preparation, layers backing layers, intermediate layers, sublayers, protective ployed, the amount layers and baryta layers in order to prevent the fogging influence of such layers.

It has been furthermore amount of sodium benzene sulfinate or seleninate necessary to produce the stabilizing efl'ect can be reduced by 60-90% if bination with the monoor polys'ulfides. pending somewhat on the type of gelatin zene sulfinate or seleninate can be reduced in many cases to 1 s the amount necessary when i used without the addition of the monoor polysulfide. It has been found that in such cases, the reduced amount of the sodium benzene sulfinate in combination with the monoor polysulfide give superior results in cleamess, grada- 'tion and keeping'quality, whereas the thus reduced amount of sulfinate, if used without the monoor polysulfide, would be entirely inadequate for producing a stabilizing eifect on the photographic emulsions.

Without in any way wishing to be bound by or limited to any particular theory as to themechanism of the additional stabilizing efliect produced by monoor polysulfides of the above class,

it is believed that this additional stabilizing effeet is either a catalytic one or is due to a chemical interaction between the sulfide compound and the sulfinate r seleninate with the possible production of a reaction product which exerts the enhanced stabilizing influence on the silver halide emulsion. The following examples will serve to further illustrate the invention, it being understood that the invention is not limited thereto:

Example I To 1 kilogram'ofa gelatino-silver-halide emulsion containing from 6 to 7% of silver halide and approximately 8% gelatin there were added as a coating final:

Cc. A 20% solution of sodium salt of p-toluene 1 sulfinic acid 15 I An alcoholic solution of morpholine disulfide of the concentration of one gram per one liter of methanol 2 5 The melted emulsion was then mixed and cast On a film base andcut intotest film lengths.

Similar test films were made with the same silver halide emulsion but omitting the addition oi either the sodium salt or p-toluene' sulfinic acid or of. morpholine disulfide. Additional similar test films were made with the same silver halide emulsion to. which had been added as a coating final the same quantity of the sodium salt of ptoluene sulfinic acid as above but omitting the morpholine disulphide. a

The fog density of each of these types of test film was determined for the freshly. prepared film and :test pieces of each type were then incubatedfor a period of six days at 50 C. It was observed that the fog density of the films treated with'p-toluene sulfinic acid to which had been added -morpholine disulfide was decreased by 50%, in the case of the freshly prepared film, and about 45%, in the case of the incubated film, of the fog density of. the films which had been treated only with p-toluene sulfinic acid.

Example II To 1 kilogram of a gelatino-silver-halide emulsion containing from 6 to 7% of silver halide and these salts are used in coming the ripening stage: discovered that the I of the stabilizing sodium ben- Similar test films were made approximately 8% gelatin there were added dur- Cc. A 20% solutionof the sodium salt of benzene seleninic acid An alcoholic solution of morpholine disulfide of the concentration of one am per liter of metha 1 film and test pieces of each type were then incubated for a period of six observed that the fog density of the films treated with benzene seleninic acid to which had been added morpholine disulfide was decreased by 50%, in the case of the freshly prepared film, and about 45%, in the case of the incubated film, the fog density of the films with benzene seleninic acid alone.

Example III To'l kilogram of a gelatinous silver halide emulsion containing 6-7% silver halide and 8% gelatin there was added during the ripening stage:

3 Cc. A 20% solution of the sodium salt of p-chlorobenzene sulfinic acid 15 Morpholine mono-sulfide in a concentrationoi 1 gram per liter of methanol The clearness of the emulsion and the keeping quality was determined in a similar mannner as described in Examplel. .Again, it was observed that both clearness and keeping quality were con-' siderably improved over an addition of the chlorobenzene sulfinic acid without the morpholine monosulfide. It may be mentioned that the morpholine monosulfide may be substituted by an equivalent amount of morpholine tetrasulflde. The same reduction as in the case of Examples 1 and 11.

Example IV To a gelatinous silver halide emulsion containing silver halide corresponding to 100 grams silver nitrate, cc. of 20% solution of sodium benzene sulfinate and 20 cc. of a solution of morpholine disulfide in a concentration of 1 gram per liter of methanol were added immediately after the precipitation of the silver halide prior to the first digestion. The emulsion was subsequently washed and after-ripened in a manner familiar to those skilled in theart.

The clearness and keeping quality of the emulsion was found to be in all cases improved aswith the addition of the without the addition same extent in the case of'Examples I andII.

Ezample V A sodium benzene sulfinate To ljki logram gelatinous silve'rhalide emulsion there was added during the ripening stage:

10 cc. of a 20% solution of sodium benzenesulfinate and 5 cc. of alcoholic solution contain- Additional similar test days at. 50 C. It was which had been treated in fog density was obtained compared to one obtained of the polys'ulfide to the ing proline disulfide in a concentration obtained as follows: 230 mg. of l-proline were suspended in approximately 70 cc. of carbontetrachloride at a temperature of 2 to -5 C. This suspension was treated with 134 mg. of sulfur mono-- chloride in the presence of 124 mg. of sodium carbonate (monohydrate) with frequent vigorous agitation. The solvent was distilled off under diminished pressure at 40-45 C. The residue was washed from the flask with absolute ethyl alcohol, filtered and the filtrate evaporated to dryness. The residue was extracted with ethyl alcohol; the extract was filtered and adjusted to a final volume of 500 cc. with ethyl alcohol. The disuliide was not isolated.

The stabilizing eifect obtained with the combination of sodium benzene sulfinate and this preparation of proline disulfid'e gave a siinilarly favor able efiect as described in detail in Example II.

Example VI To 1 kilogram of a gelatinous silver halide emulsion of high speed Portrait type ready for coating, 2.5 cc. of the followin solution was added as a stabilizer:

Part 1: 5.0 cc. solutionbenzene sulfinate (c. p.) 2.0 cc. water.

Part 2: 14 cc. methanol, 29 mg. morpholine disulfide (recrystallized. M. P. 1234).

Part 3: 4.0 cc. of 0.1 n-sulfuric. acid.

that obtained otherwise only with 1500 cc. of a 20% solution of sodium benzene sulfinate.

Similar results may be obtained when the sodium benzene sulfinate or seleninate is replaced by, for instance, naphthalene sulfinic acid, ethane suliinic acid or other sulfinic or seleninic acids such as described in U. S. P. 2,057,764. The preparation of the various monoand polysulfides such as morpholine disulflde has been described in theliterature and in U. S. P. 2,343,524. The manufacture of'these substances does not form any part of this invention.

In a similar -way to that described in U. S, P, 2,057,764, paper can be impregnated with the sodium salts of thiophene sulflnic acid to which smal1 quantities of one of the above class of monoor polysulfides have been added. Film in heterocyclic monoand polysulfides having the following formulae:

wherein R stands for an aryl radical, R1 a member of the group consisting of hydrogen, alkyl, and aryl, 1t is a positive integer, Y is a member of the group consisting of N, O, S, and CHa--, and Z represents the remaining components necessaryto complete up to a B-membered heterocyclic ring.

2. A photographic material comprising a silver-halide gelatin emulsion containing a member of the group consisting of a sulfinic acid, a seleninic acid and their salts, and an organic sulfide compound selected from the group consisting of aryl-substituted diamino and N-heterocyclic monoand polysulfides having the following formulae:

ber of the group consisting of hydrogen, alkyl, and aryl, 'n is a positive integer, Y is a member of the group consisting of N, O, S, and -CH2, and Z represents the remaining components necessary to complete up to a. B-membered heterocyclic ring.

3. A photographic material comprising a silver halide gelatin emulsion in contact with a member of the group consisting of seleninic acid, a sulfinic acid and their salts and small amounts of morpholine disulfide.

4. A photographic material comprisiig a silver halide gelatin emulsion in contact with a mem-- 5 ber of the group consisting of a seleninic acid,

contact with the paper treated in such a manner shows superior clearness as compared to paper which has received a treatment with the sodium salt of the thiophene sulfinic acid without'the monoor polysulfide.

It is within the scope of this invention to add combinations of sulflnates or seleninates and monoor polysulfides also to antihalation and surface layers, a procedure which yields results which cannot be attained when using only the sulflnates or seleninates.

What I claim as my invention and desire to secure by Letters Patent of the United States is:

1. A photographic material comprising a silver-halide gelatin emulsion in contact with a member of the group consisting of a sulflnic acid, a seleninic acid and their salts, and an organic suliide compound selected from the group consisting of uni-substituted diamino and N- a sulfinic acid and their salts and small amounts of morpholine tetrasulfide.

5. A photographic material comprising a silver halide gelatin emulsion in contact with'a member of the group consisting of anseleninic acid, a sulflnic acid and their salts and small amoun of proline'disulfide.

6. A photographic material comprising a silver halide gelatin emulsion containing a, member of the group consisting of a sulflnic acid, a seleninic acid and their salts, and small amounts or morpholine disulflde.

7. A photographic material comprising a silver halide gelatin emulsion containing a member of the group consisting of a sulflnic acid, a seleninic acid and their salts, and small amounts of morpholine tetrasulflde.

8. A photographic material comprising a silver halide gelatin emulsion containing a member of the group consisting of a sulflnic acid, a seleninic acid and their salts, and small amounts of proline disulflde.

9. A photographic material comprising a silver 

